Sum of last 3 entered columns formula?

[krispartsbadger]

I track my month to month financials and use =LOOKUP(99^99,A3:L3) in a column to keep track of the month to date total. What would be a formula to calculate the sum of the 3 previous months?

 

[gargamalebarbosa]

Coudl you try
SUM(OFFSET(A3,,COUNTA(A3:L3)-3,,3))

 

[Siddharth Rout]

I track my month to month financials and use =LOOKUP(99^99,A3:L3) in a column to keep track of the month to date total. What would be a formula to calculate the sum of the 3 previous months?

I have shown you how to do it for the last 3 filled cells down a column HERE

For last 3 filled cells across a row you can use

=IFERROR(SUM(OFFSET(A2,0,LARGE(IF(B2:M2<>"",COLUMN(B2:M2))-1,3),1,(13-LARGE(IF(B2:M2<>"",COLUMN(B2:M2))-1,3)))),"-")

Few things worth mentioning.

1. This formula caters to blank cells in between if there are any.
2. This is for 12 cells. Amend the formula accordingly.
3. If there are less than 3 values, then it doesn't error out.

 

[krispartsbadger]

What am I doing wrong? I've copied what your formula, but I get a "-" in A4

 

[Siddharth Rout]

It works for me.

Try the formula without the IFERROR. See what error do you get?

=SUM(OFFSET(A2,0,LARGE(IF(B2:M2<>"",COLUMN(B2:M2))-1,3),1,(13-LARGE(IF(B2:M2<>"",COLUMN(B2:M2))-1,3))))